This invention relates to a superprecision positioning device which can position a movable output shaft with high accuracy and with superfineness by movement in a two-dimensional surface caused by a composite eccentric rotor and rotation of an output shaft.
A conventional precision positioning device having a relatively narrow range and being heretofore generally known is designed so that where a one-dimensional surface is translated, a ball screw and a linear guide are combined, and the ball screw is rotated and moved by means of a pulse motor to effect positioning. The two-dimensional positioning device is used with the aforesaid one-dimensional positioning mechanism disposed perpendicular thereto.
A rotation positioning device for rotation indexing or the like used recently in machining or the like uses no gear and reduction device, but an electrically direct driving device has been developed which directly drives, rotates and controls an axial table.
Recently, in industrial robots used to assemble heavy articles, positioning of high torque and high precision has been required. Furthermore, in focus control of a laser beam and in a wiring process for integrated circuits, superfine movement is also required. In light of this, the development of a positioning device having a higher precision and capable of being used in the aforementioned fields has been demanded.
However, in the conventional positioning devices, the rotation of the pulse motor is converted into a linear motion by the ball screw to effect positioning in a one or two-dimensional surface. Problems incurred include backlash caused by a thread pitch of the ball screw, and thus repeatable precision in micron units cannot be obtained. In addition, in the rotation positioning device of the aforementioned electric direct drive, positioning of rotation may be carried out with relatively high precision but this merely handles positioning of rotation. This poses a problem in that the device cannot be applied to positioning of a two-dimensional surface by translational movement.